“I am devastated by the brutal murder of Xulhaz Mannan and another young Bangladeshi,” said US Ambassador Marcia Bernicat.

“We abhor this senseless act of violence and urge the government of Bangladesh in the strongest terms to apprehend the criminals behind these murders,” she added.

The other victim, identified by Bangladeshi media as Tanay Mojumdar, also worked at Roopbaan

BBC Bengali Service editor Sabir Mustafa said staff at Roopbaan, a magazine and activist group for the Lesbian, Gay, Bisexual and Transgender (LGBT) community that had not been condemned by the government and received some support from foreign embassies, had been careful to protect their identities but had not believed their lives were at risk.

Suspected extremists in Bangladesh are gaining a sense of security that they can carry out killings with impunity, he says.

A British photographer who knew Mr Mannan and the other victim, known as “Tonoy” and named in Bangladeshi media as Tanay Mojumdar, said they and other friends had set up Roopbaan with the aim of spreading tolerance.

Homosexuality is technically illegal in Bangladesh and remains a highly sensitive issue in society.

Both men were openly gay and believed that if more gay Bangladeshis came out then the country would have to accept them, the photographer said.

APMr Mannan and another man were killed at his apartment building.

They were also were behind the annual “Rainbow Rally”, held on Bengali New Year, 14 April, since 2014. This year’s rally was banned by police as part of widespread security measures.

“Both were extremely gentle, non-violent and aware that being openly gay and active in their work was a personal danger,” the photographer said.

Their killings were likely to spread fear among Bangladesh’s gay community, he said.

“Until a year ago the only threat to coming out was shame of the family and having to start a new life elsewhere in Bangladesh. Now it’s one of danger,” he said.

Long line of killings

Meanwhile Bangladesh’s best known blogger said he had received a death threat on Sunday.

Imran Sarker, who led major protests by secular activists in 2013 against Islamist leaders, said he had received a phone call warning that he would be killed “very soon”.

AFP/GettyStudents have protested against the previous killing, which saw a university professor hacked to death on Saturday